1. Field of the Invention
This invention generally relates to a rotary head drum device. This invention particularly relates to a rotary head drum device for apparatuses such as a video tape recorder and a data streamer.
2. Description of the Related Art
In a prior-art recording and reproducing apparatus such as a data streamer or a video tape recorder of a helical scan type, a plurality of rotary heads are mounted on the outer circumferential surface of a rotary drum at predetermined angular intervals, and a magnetic tape (a recording medium) is wrapped on the outer circumferential surface of the rotary drum in a prescribed angular range along a part of helix. During operation of the prior-art apparatus, the magnetic tape is fed relative to the rotary drum in a given direction, and is scanned by the rotary heads. Specifically, during a recording mode of operation of the prior-art apparatus, the rotary heads record an information signal on the magnetic tape while forming slant recording tracks thereon. During a playback mode of operation of the prior-art apparatus, the rotary heads reproduce the information signal from the recording tracks on the magnetic tape.
It is known to design and arrange the rotary heads so as to differentiate azimuth angles of adjacent recording tracks on the magnetic tape. In this case, it is unnecessary to provide guard bands between recording tracks. The absence of guard bands enables the magnetic tape to be efficiently used in the recording of an information signal.
Some of such helical-scan recording and reproducing apparatuses for guard-band-less recording are designed to be operable in any one of many different modes and to be compatible with another recording and reproducing system. These apparatuses tend to have an increased number of rotary heads on a rotary drum.
There is a physical limitation on the number of rotary heads which can be mounted on a rotary drum. In view of this limitation, advanced rotary head drum devices have been developed. For example, Japanese published unexamined patent applications 5-28445, 7-98827, 7-220252, and 8-124130 disclose rotary head drum devices having a quadruple head structure in which four rotary heads are provided in one window in a rotary drum, and are arranged at respective different phases with respect to the direction of rotation of the rotary drum.
Some rotary head drum devices include double azimuth heads referred to as DA heads. The DA head has two head cores which are provided in one window in a rotary drum, and which are connected with a common support on the rotary drum. For example, Japanese published unexamined patent applications 5-128452, 8-297823, 9-161247, and 11-161925 relate to head shapes, crosstalk, inter-core distances, and head-touch states in DA-head structures.
There are known rotary head drum devices including pair heads. The pair head has two head cores which are provided in one window in a rotary drum, and which are supported independently of each other.
Digital-signal recording and reproducing apparatuses conforming to the D-VHS (trademark) standards are designed so that they can also implement analog VHS (trademark) recording and playback. To implement analog VHS recording and playback in addition to D-VHS recording and playback, a rotary drum in the D-VHS apparatus has an increased number of rotary heads.
A conceivable rotary head drum device which is not prior art against this invention has an increased number of high-performance rotary heads on a rotary drum. Since the high-performance rotary heads are expensive, the conceivable rotary head drum device is high in cost. Using inexpensive rotary heads instead of the high-performance rotary heads causes poor operation characteristics of the conceivable device.
It is an object of this invention to provide a low-cost high-performance rotary head drum device.
A first aspect of this invention provides a rotary head drum device comprising a rotary drum rotating at a given speed, and a plurality of rotary heads mounted on the rotary drum for scanning a magnetic tape fed in a given direction and wrapped on an outer circumferential surface of the rotary drum in a predetermined angular range along a part of helix, the rotary heads recording an information signal on the magnetic tape while forming recording tracks in a guard-band-less structure on the magnetic tape during recording, the rotary heads reproducing the information signal from the recording tracks on the magnetic tape during playback. The rotary heads comprise first and second rotary heads for a low-frequency-range information signal, the first and second rotary heads being opposed to each other diametrically with respect to the rotary drum and being different from each other in azimuth angle; a third rotary head for digital signals in frequency ranges higher than a frequency range of the low-frequency-range information signal, and for first and second operation modes being different from each other in data transmission rate; a fourth rotary head for a digital signal in the second operation mode, the fourth rotary head being opposed to the third rotary head diametrically with respect to the rotary drum and being equal in azimuth angle to the third rotary head; a fifth rotary head for a digital signal in the first operation mode, the fifth rotary head being substantially opposed to the third rotary head diametrically with respect to the rotary drum and being different from the third rotary head in azimuth angle, the fourth and fifth rotary heads being in a double azimuth head structure; and sixth and seventh rotary heads for a digital signal in the second operation mode, the sixth and seventh rotary heads being opposed to each other diametrically with respect to the rotary drum and being equal to each other in azimuth angle.
A second aspect of this invention is based on the first aspect thereof, and provides a rotary head drum device wherein the first, third, and fourth rotary heads are equal to each other in azimuth angle, wherein the second, fifth, sixth, and seventh rotary heads are equal to each other in azimuth angle, and wherein scanning trajectories formed by the third and sixth rotary heads and corresponding to two adjacent parallel tracks, and scanning trajectories formed by the fourth and seventh rotary heads and corresponding to two adjacent parallel tracks alternately occur during the second operation mode.
A third aspect of this invention provides a rotary head drum device comprising a rotary drum; first and second rotary heads provided on the rotary drum and opposed to each other diametrically with respect to the rotary drum, the first and second rotary heads being different from each other in azimuth angle and having frequency response characteristics suited for an information signal in a given frequency range; a third rotary head provided on the rotary drum and having a frequency response characteristic suited for a digital signal in a frequency range higher than the frequency range of the information signal; a fourth rotary head provided on the rotary drum and opposed to the third rotary head diametrically with respect to the rotary drum, the fourth rotary head being equal in azimuth angle to the third rotary head and having a frequency response characteristic suited for a digital signal in a frequency range higher than the frequency range of the information signal; a fifth rotary head provided on the rotary drum and substantially opposed to the third rotary head diametrically with respect to the rotary drum, the fifth rotary head being different from the third rotary head in azimuth angle and having a frequency response characteristic suited for a digital signal in a frequency range higher than the frequency range of the information signal, the fourth and fifth rotary heads being in a double azimuth head structure; and sixth and seventh rotary heads provided on the rotary drum and opposed to each other diametrically with respect to the rotary drum, the sixth and seventh rotary heads being equal to each other in azimuth angle and having frequency response characteristics suited for a digital signal in a frequency range higher than the frequency range of the information signal.
A fourth aspect of this invention is based on the third aspect thereof, and provides a rotary head drum device wherein the first, third, and fourth rotary heads are equal to each other in azimuth angle, and wherein the second, fifth, sixth, and seventh rotary heads are equal to each other in azimuth angle.
A fifth aspect of this invention is based on the third aspect thereof, and provides a rotary head drum device wherein the third and sixth rotary heads form scanning trajectories corresponding to two adjacent parallel tracks, and the fourth and seventh rotary heads form scanning trajectories corresponding to two adjacent parallel tracks.